can anyone explain what causes this?

[pepperbear]

http://www.wimp.com/recordpropellers/

seemingly unintended visual effect.

[RandomThoughts]

1. Wow, that is a huge dispatch.

Things going to get interesting.

Thanks.



Great post, hit next 4 times.

A ww2 trumpeter talks about war experiences.
http://www.wimp.com/remarkableexperience/


Although no reason to be afraid.

[nolabear]

2. Well, when you talk about a TV picture flipping on a TV show

or a fan looking like it's standing still under flourescent lighting, it has something to do with the synchronization of the timing of the two, so I suppose it must be similar. And we've just reached the end of my comprehension, tenuous as it is. Thank you.

[struggle4progress]

3. That's caused by recording an airplane propeller with a cell phone

To put it in more scientific and mathematical terms: recording an airplane propeller with a cell phone causes that

[jobycom]

5. Hm, that's confusing. Would you say then, that

the cell phone recording the propeller causes that? Or am I way off?

[struggle4progress]

6. That's approximately right, though you've expressed it in layman's terms

[jobycom]

7. .

:rofl: (i needed the laugh. :) )

[pepperbear]

8. so what you're saying is it's the "recording an airplane propeller with a cell phone Phenomenon"...

...first discovered by noted Scotch-Swedish aeronaut Dr. Hamish Von Bbjornstrand in 1927?

[struggle4progress]

11. I don't think they had phenomena back in 1927. IIRC phenomena were invented around 1930

[jobycom]

4. I think it's a reflection.

I took a picture of an aquarium through a viewing window below the water's surface, and the picture created a mirror image with the inner surface of the water so that everything was doubled. It didn't look that way IRL, just in the picture, so it had something to do with the way the picture was digitally interpreted--probably the surface gave the camera a stronger image to capture than the light above it, even though to the naked eye you couldn't see the surface reflection.

If you look at your clip, as the blade rolls up from underneath, you can see a shadow of a blade coming down to meet it. Just as the shadow blade "connects" with the blade from below coming up, the boomerang image is created in the center, then the image sinks away. I think the camera is capturing a reflection in the window combined with the real blade where the image bends--the upper blade is the reflection of the lower blade meeting at a point on the window. Or maybe they are both reflections. Or maybe they are reflecting off the camera lens. Either way, once the image forms, the camera's frame capture makes it look like it's slowing down as it captures successive blades in their rotation, like recording a fan.

Something like that, anyway. :) I got a headache from looking as long as I did.

[The Midway Rebel]

9. The Persistence of Vision

http://en.wikipedia.org/wiki/Persistence_of_vision

Also demonstrated by the rubber pencil trick.

http://www.mrmagician.co.uk/RubberPencil.html

[baldguy]

10. It's called a rolling shutter effect.

http://blancer.com/tutorials/i-phone/82584/rolling-shutter-effect-can-make-stunning-iphone-photos/



A cell phone camera doesn't record the entire image when it takes a picture or a video frame. The image is scanned from one side to the other, which takes a certain amount of time.